The ankle exercise board can be used as an instrument quantifying human balance skills and learning strategies. However, this requires an appropriate recording of its movement. Using the theory of integrated navigation systems as well as simulation and experimental data, a corresponding motion measurement system was developed and qualified: Modelling the vehicle kinematics is an essential design task of such integrated systems. It has to consider both the vehicle motion and the mechanical meaning of the used measurements. Until now, a rigid body with three translational and three rotational degrees of freedom represents the typical model applied. However, for an ankle exercise board, which is in fact a hemisphere oscillating on the floor, the design of a special attitude measurement system is possible. It is based on a model with only three rotational degrees of freedom and on considering spatially distributed accelerometers. The utilised data fusion employs nevertheless the same principle as for integrated navigation systems. It comprises additionally three micro-mechanical gyros as well as a Kalman filter estimating the three Euler angles of the board and sensor calibration values. To illustrate the application of the system, aspects of observing the rehabilitation after ankle and knee injuries conclude the paper.
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